Recently, researches on hybrid type construction equipment, which improves fuel efficiency by storing surplus power of an engine in a battery, and supplying power from the battery to the engine that does not have sufficient power so as to cope with a rapid increase in oil price, are being actively conducted.
A system, which uses the engine and an electric motor as a common power source as described above, and has an electrical energy storage device, is referred to as a hybrid system. For example, as the hybrid system, there is a hybrid system for heavy equipment such as a hybrid vehicle, and an excavator.
FIG. 1 is a configuration diagram of an electric power conversion device for general hybrid construction equipment.
As illustrated in FIG. 1, an electric power conversion device for hybrid construction equipment includes an engine auxiliary motor 110, an engine side inverter 111, a swing motor 120 having a brake, a swing side inverter 121, an ultracapacitor 130, and a converter 131.
The engine side inverter 111 operates the engine auxiliary motor 110 using a motor or an electric generator.
The swing motor 120 operates an upper swing body of a hybrid excavator. The swing side inverter 121, which operates the swing motor 120, performs an acceleration operation and a deceleration operation depending on lever control by a user who manipulates the hybrid excavator. The swing side inverter 121 operates the swing motor 120 using a motor at the time of an acceleration operation. In contrast, the swing side inverter 121 operates the swing motor 120 using an electric generator at the time of a deceleration operation. That is, the swing side inverter 121 converts rotational inertial energy of the upper swing body of the hybrid excavator into electrical energy.
The ultracapacitor 130 serves to store electrical energy, and is connected with the converter 131 that controls a charge operation and a discharge operation.
FIG. 2 is a flowchart of an exemplary embodiment regarding a failure occurrence process in an electric power conversion device for general hybrid construction equipment.
As illustrated in FIG. 2, the electric power conversion device in the related art stops all operations when failure occurs in the electric power conversion device (S202).
Specifically, the electric power conversion device turns off the engine side inverter 111 of the engine auxiliary motor 110 (S202). In addition, the electric power conversion device turns off the swing side inverter 121 of the swing motor 120 (S206). Next, the swing motor 120 undergoes a regeneration process of the swing motor 120 (S208), and Vdc is in an overvoltage state (S210). In addition, the electric power conversion device turns off the converter 131 at the ultracapacitor (UC) 130 side (S212).
As described above, in the hybrid excavator, the upper swing body is freely rotated before a braking operation when the electric power conversion device is stopped, unlike a hydraulic excavator, and thus there is a problem in that a risk of an accident is greatly increased in this case. When the swing body is continuously rotated, there is a problem in that a peripheral area of the work environment may be damaged.
In order to reduce the aforementioned damage, the rotation of the swing body is blocked, and a swing brake is operated until inertial energy is exhausted. A brake control manner in the related art produces a brake off command when a swing speed is a predetermined value or less. The hydraulic brake is operated with a predetermined delay after the brake off command is generated. In this case, there is a problem in that when the braking operation is immediately performed using a mechanical swing brake in a case in which a large amount of inertial energy remains because a speed of the swing body is high immediately before failure occurs, impact may be applied to a user, and the excavator may be turned over on a slope.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.